Sum Root to Leaf Numbers

描述

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

  1.     1
  2.    / \
  3.   2   3

The root-to-leaf path 1->2 represents the number 12.The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

分析

无

代码

  1. // Sum root to leaf numbers
  2. // 时间复杂度O(n)，空间复杂度O(logn)
  3. class Solution {
  4. public:
  5.     int sumNumbers(TreeNode *root) {
  6.         return dfs(root, 0);
  7.     }
  8. private:
  9.     int dfs(TreeNode *root, int sum) {
  10.         if (root == nullptr) return 0;
  11.         if (root->left == nullptr && root->right == nullptr)
  12.             return sum * 10 + root->val;
  14.         return dfs(root->left, sum * 10 + root->val) +
  15.                 dfs(root->right, sum * 10 + root->val);
  16.     }
  17. };

原文: https://soulmachine.gitbooks.io/algorithm-essentials/content/cpp/binary-tree/recursion/sum-root-to-leaf-numbers.html